Manufacture of bituminized felts



Aug. 4, 1936. M. o. SCHUR ET AL MANUFACTURE OF BITUMINIZED FELTS FiledJan. 4, 1933 QQOQUGOOOO vex/67% Patented Aug. 4, 1936 UNITED [STATES]MANUFACTURE OF BITUMINIZED FELTS Milton 0. scam: and Walter 1.. Beam,Berlin, N. IL, assignors to Brown Company, Berlin, N. H., a corporationof Maine Application January i, 1933, Serial No. 650,100

7 Claims.

This invention relates to the manufacture of bituminized felts such asare to servefor roofing, flooring, and similar purposes. Such bitumi--nized felts are usually made by producing the felt essentially fromcellulose fiber 'on machinery of the paper-making, type and then runningthe felt through one or more baths of molten asphalt which entersuniformly into and throughoutthe felt as an impregnant impartingwater-repellency, strength, tear resisistance, and other desiredqualities to the product.

It has been found that bituminized felts of greatly improvedcharacteristics, including strength and tear resistance, may be had byusing refined cellulose pulp in substantially unhvdrated condition as acomponent in the. feltmaking furnish. Indeed, it has been found possiblethrough the use of refined wood pulp insubstantially unhydratedcondition as the main raw material for felt-making, to arrive at feltswhich, notwithstanding their lack of high strength and tear resistancein their raw 'or unimpregnated state, yieldbituminized sheets which arepracticallytearproof; In applying this knowledge a toactual practice,however, it was foundthat there was great variability in the toughnessof bituminized sheets made at different times, despite the fact that allwere prepared in the same way, that is, from the same kinds and amountsof fiber and impregnant. In some instances, the bituminized sheet wouldhave remarkably high toughness, whereas in other instances, abituminized sheet of similar composition. would 'be of comparativelypoor tear resistance and other physical qualities.

peared to be the freakish and inconsistent results heretofore realizedin preparing the bitu- 50 remarked that the hot molten asphalt, withwhich the felt contacts during the bituminizing operation, evi dentlyexpels all the free moisture present in the felt, so that the toughness55 developed in the bituminized sheet heretofore We'have discovered thatthe physical qualities minized sheets. In this connection, it is to be 1depended upon the moisture which the bituminized felt picked up from theatmosphere while passing from the saturator to the windup roll.. Oncewound up into a roll, the sheet material constituting the interior ofthe roll re- 5 mains practically unchanged even "though the surfacelayers of the roll undergo improvement by virtue of being humidified bythe moisture in the atmosphere.

In accordance with the present invention, 10v

therefore, the bituminized sheetis humidified with suflicient moistureso that it becomes possessed of the maximum p0 ential strength, tearresistance, and other physic l qualities. In the case of a'bituminizedsheet designed for roofing purposes, the humidification of the sheet maybe efiected from either or both faces, whereas a bituminized sheet toserve as a fioor covering may be humidified from its back face after ithas undergone ornamentation as with linseed-oilpaint and has gonethrough the baking oven wherein the linseed-oil-paint is oxidized ordried, thereby avoiding any tendency for the moisture to impair thelinseed-oil-paint or other omamen-- tal finish. In both cases, however,the finished sheet is wound up tightly as a roll wherein the moisturehas ample opportunity to diffuse with minimum loss by evaporation intothe air. In some instances, as when the roll is to be stored for aconsiderable periodin a dry atmosphere, it may be desirable to keep therolls sealed from the atmosphere as by wrapping them in moistureproofpaper, cellophane, or the like, thereby preserving the bituminized sheetthroughout in the proper humor until it is to be used. Once havingbecome humidified throughout, the bituminized. sheet parts reluctantlywith its moisture content and, under most prevailing atmosphericconditions, retains sufiicient moisture therein to remain at its maximumpotential toughness. Once having been used or laid, it is not soessential that the bituminized sheet possess optimum qualities, but evenwhen it is exposed to comparatively dry atmosphere, it 1oses but littleof its toughness, as it practically never meets in service withconditions underwhich it becomes dehydrated to the bone-dry conditionwhich it sometimes acquires as a'result of the bituminizing operationand wind-up into a roll before it has had an opportunity to pick upmoisture from the atmosphere. v

While there are various ways in which to humidify thebituminized sheet,as for instance by exposing it'to an atmosphere saturated with watervapor, it is preferable to spray a fine mist rollshad stood about for aweek, samples were Y of water onto either or both faces of the sheetimmediately before it is wound up tightly as a roll. In the case of asheet which is being impregnated in a roofing machine, spray nozzles maybe set up across the machine near the windup roll and water may besupplied to the nozzles by a positive pressure pump geared to themachine so that the sheet will receive on either or both its faces theappropriate amount of water as it is being wound up. Although the exactamount of water added to the sheet does not appear to be a criticalmatter, it is preferable that the sheet take on at least about to ofWater, based on the weight of fiber, as this amount of moisture ensuresa development in the sheet of optimum physical qualities.

In order to demonstrate the beneficial effects attending the practice ofthe present invention, I shall takeas a concrete example, a tightlywound roll of smooth-surface roofing which was prepared without havingundergone humidification. Although this roofing contained as its base afelt whereinto refined wood pulp in substantially unhydrated conditionhad entered as raw material, it was found that the interior of the rollwas much lower in tear resistance than the exterior of the roll whichhad evidently picked up moisture from-the atmosphere and had thus beenimproved in its physical qualities. This roll was unwound and sprayed onits surface with a very fine mist of water as it was being tightlyrewound. For purposes of comparison, a second similar roll of roofingwas unwound and rewound under similar conditions without, however, the

addition of moisture to the sheet. After both taken from the interior ofeach roll and tested. The results follow:-

Muisteued Dry sample 1 Sample Starting tear 5. 0 7. 5 Running tear- 19003300 Mullen test 225 250 The foregoing values for starting tear andrunning tear are expressed in arbitrary units.'

It is thus seen that the improvements brough about through the sprayingof. water onto the sheet are striking and highly important. The

fact is that whereas the sprayed sample was prac-' tically tear-proof,the other was comparatively easily torn by hand. There was no evidenceof free moisture on the sprayed sample.

On the accompanying drawing,- Figure 1 illustrates diagrammatically andconventionally apparatus, including spray nozzles,

such as may be used in practicing the present invention.

Figure 2'is. a fragmentary plan view of the apparatus showing a bank ofnozzles arranged to spray, across a face of the sheet.

The apparatus shown in Figure 1 is intended to illustrate the practicewhich may be adopted in preparing roofing in accordance with the presentinvention As shown therein, a roll I of raw felt may be mounted forunwinding at one end sheet may be looped as between upper guide rolls 5and lower guide rolls 6 as it is passing through the vat 3. Uponemerging from the vat, the bituminized sheet may be passed through apair of squeeze rolls 1 which serve to remove excess asphalt from thesheet, the excess flowing back to the bath 4. The squeezed sheet maythen be cooled so as to cause a congelation of its asphalt content. Thesheet is shown passing upwardly from the rolls 1 to a set of. rolls 8 onwhich the sheet is festooned with sufficient sheet area exposed to theatmosphere to ensure a congelation of the asphalt. Any other suitablecooling means, such as hollow drums through which cold water passes, maybe provided for this purpose. The cooled sheet may then pass into ahumidifying chamber 9, wherein both its surfaces may receive a fine mistof water delivered from a series of spray nozzles I0 arrangedimmediately above and below the sheet. The upper and lower bank of spraynozzles each communicate with a manifold II extending across the sheetand supplied with water under pressure from a suitable source (notshown). After thus being sprayed, the sheet may remainin the chamber asloops defined by a series of rolls l2, thereby ensuring good difiusionof the free water into the interior of the sheet before it emerges fromthe chamber. The humidified sheet may finally be rewound tightly into aroll l3 for storage and shipment. I

While it is difiicult to explain with accuracy the role which moistureplays in developing the qualities desired in the bituminized sheet,nevertheless it is probably the case that the moistened fibers are morepliant or flexible than fibers which are dehydrated orbone-dry. In abituminized sheet containing a felt base, whose fibers are in a refinedand substantially unhydrated condition, the tear resistance and otherdesired qualities apparently hinge upon the ability of the fibers toglide or move relatively when a tearing stress is applied to the sheet.In other words,

a tearing stress cannot be concentrated locally and cause rupture ortearing of the sheet so easily as is the case when the fibers are bondedtogether by the gelatinized or'hydrated cellulose present in a sheetprepared from beaten or hydrated pulp, or from pulp which, by virtue ofimpurities present therein, tends to form a comparatively dense andimpenetrable sheet whose fibers are stuck together by the hydratedimpurities. The function of the moisture is evidently that of improvingthe pliancy or flexibility of the fibers of the sheet, so that theirtearing is inhibited, as well as to enhance the pliability of thesaturated sheet as a whole, rendering it less brittle.

While the. principles of the present invention .are applicable tovarious kinds of bituminized felted sheets, they are, as alreadyindicated, more especially of value in connection with bituminized feltscontaining refined cellulose pulp in substantially unhydrated conditionas an essential tuminized rag felts,inevitably possess a low order oftoughness and can be improved comparatively little in this respect. Therefined cellulose pulp employed in the sheets of the present inventionmay be prepared as by exposing the usual chemical wood pulps, e. g.,kraft or sulphite pulp, to the action of alkaline liquors underconditions resulting in an extraction of asubstantial proportion of thenon-aloha cellulose components from with siccative liquid coatingmaterial one face.

fined. In any case, however, the pulp, refined or otherwise, enteringinto the felt-making furnish should be maintained in a substantiallyunhydrated condition in order to yield a bituminized sheet of thedesired toughness. Even when extraneous binders, such as starch,gelatinized cellulose, etc., are added to the felt-making furnish so asto improve the flexing qualities of the felt, the course of keeping therefined cellulose pulp component in substantially unhydrated conditionshould be pursued in order to arrive at a bituminized felt having thedesired physical characteristics. The moisture applied to the surface ofthe bituminized sheet undoubtedly works its way into the sheet throughthe tiny, almost microscopic imperfections in the bituminous filmsdeposited on the surface of the sheet and on the fiber surfaces. Thisdiffusion of moisture into the sheet is, as already indicated, quiterapid, but it may be desirable to add to the water sprayed onto thesheet surface a small quantity, say, 0.05% of a fungicide, such assodium fluoride, sodium phenol-phenolate, mercuric chloride, or thelike, so as to discourage molding which might under some circumstancesotherwise occur while water'is diffusing uniformly into and throughout atightly rolled sheet.

We claim:-

.1. A method which comprises ornamenting of a bituminized sheetcontaining interfelted celhumidifying the sheet from its unornamentedface.

2. A method which comprises ornamenting with linseed-oil-paint one faceof a bituminized sheet containing interfelted cellulose fiber, bak- 5ing the sheet, and introducing moisture into the sheet through itsunornamented face.

3. A method which comprises ornamenting with linseed-oil-paint one faceof, a bituminized sheet containing interfelted cellulose fiber, bakingthe sheet, spraying water onto the unornamented face of the sheet, andwinding the sprayed sheet into a roll.

4. A floor-covering consisting of a bituminized felt comprisingcellulose-fiber carrying an ornamental coating on one face and having atleast about 5% to 10% of water, based on the weight of fiber,substantially uniformly distributed therethrough.

5. A floor-covering consisting of a bituminized 20 felt comprisingcellulose fiber carrying linseedoil-paint ornamentation on one face andhaving at least about 5% to 10% of water, basedon the weight of fiber,substantially uniformly distributed therethrough.

6. A rolled'sheet of floor-covering consisting of a bituminized feltcomprising substantially unhydrated cellulose fiber having an alphacellulose content of at least about. 93%, said covering carryinglinseed-oil-paint ornamentation 30 on one face and having at least about5% to 10% of water, based on the weight of fiber, substantiallyuniformly distributed therethrough.

'7. A method which comprises bituminizing a felt containing refinedcellulose pulp of an alpha cellulose content of at least about 93% andin a substantially unhydrated condition, and humidifying the bituminizedfelt to a moisture content in an amount of at least about 5%, based; onthe weight of pulp, suflicient to produce therein optimum starting andrunning tear resistance and toughness characteristics.

MILTON O. SCHUR.

WALTER L. HEARN.

